Three speed circuit for hydraulic tool

A hydraulic device having a mechanical input and a mechanical output, comprising:

• a pump having a housing including a pump bore and a pump piston disposed to move linearly within said pump bore and to develop pressure on fluid occupying said pump, said pump piston having a rear face, an input shaft projecting from said pump rear face, and a front face, said pump bore having a pumping chamber exposed to said front face of said pump piston and a rear chamber exposed to said rear face of said pump piston;
• a ram having a ram housing including a ram bore and a ram piston disposed to move within said ram bore, said ram piston having a front face, an output shaft projecting from said front face, and a rear face, said ram bore having a front chamber exposed to said front face of said ram piston and a drive chamber exposed to said rear face of said ram piston;
• and
• fluid circuitry communicating between said pump bore and said ram bore such that fluid pressure developed within said pump is imposed on said ram piston, said fluid circuitry disposed to move said ram piston selectively at three speeds with corresponding magnitudes of force relative to a speed of said pump piston, said fluid circuitry including valves disposed to effect transition from one said speed to another said speed automatically, said fluid circuitry including a primary supply subcircuit conducting fluid from said pumping chamber of said pump to said drive chamber of said ram and including a check valve opposing backflow from said drive chamber to said pumping chamber, a low speed subcircuit disposed to conduct fluid under pressure from said pumping chamber of said pump to said rear chamber of said pump, said low speed subcircuit having a low speed subcircuit control valve operably controlling said low speed subcircuit, and a high speed subcircuit disposed to conduct fluid under pressure from said front chamber of said ram to said drive chamber of said ram, said high speed subcircuit having a high speed subcircuit control valve operably controlling said high speed subcircuit,
• said high speed subcircuit control valve being a pressure responsive valve disposed to open said high speed subcircuit responsive to pressures prevailing within said front chamber of said ram exceeding a first predetermined threshold pressure and to close said high speed subcircuit responsive to pressures below said first predetermined threshold pressure, and
• said low speed subcircuit control valve being pressure responsive valve disposed to open said low speed subcircuit responsive to pressures prevailing within said pumping chamber exceeding a second predetermined threshold pressure and to close said low speed subcircuit responsive to pressures below said second predetermined threshold pressure.